The term Diamond Like Carbon (DLC) describes a group of materials comprising carbon with structures and properties resembling that of diamond. Some examples of Diamond Like Carbon coatings are a-C, a-C:H, i-C, ta-C and ta-C:H coatings.
As DLC has many attractive properties including high hardness, chemical inertness, high thermal conductivity, good electrical and optical properties, biocompatibility and excellent tribological behavior, DLC has attracted a considerable interest as coating material.
A rough classification of DLC coatings is given by the fractions of sp3 bonding. Tetrahedral carbon coatings have a high fraction of sp3 bonded carbon, whereas amorphous carbon coatings such as a-C or a-C:H have a lower fraction of sp3 bonding and a higher fraction of sp2 bonding.
A second classification is given by the hydrogen content. The DLC coatings can be classified in non-hydrogenated coatings (ta-C and a-C) and hydrogenated coatings (ta-C:H and a-C:H).
The group of tetrahedral carbon coatings shows many interesting properties like a high hardness (resembling the hardness of diamond) and a high Young's modulus. These properties make tetrahedral carbon coatings ideal for many challenging wear-resistant applications.
A disadvantage of tetrahedral carbon coatings is their high roughness. In case tetrahedral carbon coatings are used as tribological coating, the wear on the counterbody can be unacceptable high.